System and method for sterilization of a liquid

ABSTRACT

Apparatus and method for sterilization of liquid includes a liquid container containing a liquid and having a piezoceramic ring that is connected to a power supply system. Power supply system supplies electric signals to the piezoceramic ring that are transformed into mechanical waves and cause vibrations in the liquid.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Patent Application No. 60/324,281, filed Sep. 25, 2001,and claims priority under 35 U.S.C. § 120 of U.S. patent applicationSer. No. 10/254,014, filed Sept. 25, 2002.

FIELD OF THE INVENTION

The present invention relates to methods and apparatuses forsterilization of liquid, and more particularly, to such a method andapparatus that utilizes hydrodynamic focused and scanning cavitation.

BACKGROUND OF THE INVENTION

Various methods have been employed for sterilization and purification ofliquid. For example, UV radiation, disinfection by biocides andpasteurization have been used for water sterilization. Ultraviolet (UV)treatment has been used to disinfect clear water as described in U.S.Pat. Nos. 3,634,025; 3,700,406; 3,837,800; 3,889,123; 3,894,236;4,471,225 and 4,602,162. Each of these U.S. patents describes a methodfor sterilization of water-based fluids. The principal idea behind thesetechniques is typically that UV radiation penetrates the clear liquid tokill offending microorganisms. UV has been also used in combination withmagnetic treatment (e.g. U.S. Pat. No. 5,997,812) by passing the fluidthrough a magnetic field followed by exposure of the fluid to adisinfecting amount of ultraviolet radiation. The conventionaltechnology of UV treatment is limited because systems made of quartzhave a tendency to foul easily and maintenance costs are high.

Another approach to disinfect water is by adding appreciable levels ofvarious biocide fluids to kill and inhibit the growth of microorganisms(e.g. U.S. Pat. No. 3,230,137). However, people exposed to biocides mayexperience allergic reactions or other problems. In short, althoughbacterial counts can be reduced over the short term, biocides are oftenmore problematic than the microorganisms themselves.

Another method for the disinfection of fluids is pasteurization. In thisprocess, fluids are heated to a pasteurizing temperature for a requiredperiod of time and subsequently cooled to an operating temperature. Thisprocess is energy intensive and the costs resulting from the heating andcooling steps are high.

Various other methods for sterilization, such as sterilization by ozoneor H₂O₂, exist. However, these are either expensive, hazardous or notsufficiently effective.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide apparatus and methods forliquid sterilization based on focused acoustic vibration waves createdin the liquid.

Embodiments of the invention relate to an apparatus and system forsterilization of liquid including at least one container suitable forcontaining a liquid and including an ultrasonic vibratable element.

According to further embodiments of the present invention the system mayfurther include a power supply system operatively connected to thevibratable element. The power supply system may be adapted to supplyelectric waves having a preselected frequency or frequency range to thevibratable element.

According to some embodiments of the present invention the ultrasonicvibratable element may include a piezoceramic material. The piezoceramicmaterial may be at least partially coated with a substantiallyconductive material. The conductive material may be operativelyconnected to the power supply system.

According to some embodiments of the present invention, the electricwaves produced by the power supply system may have a frequency thatsubstantially matches the resonance frequency of a system formed by theliquid, the cavity within which the liquid resides and the ultrasonicvibratable element. The electric wave may cause the ultrasonicvibratable element to oscillate. The oscillation of the vibratableelement may be dependent upon the frequency or the frequency range ofthe electric waves, which may either be continuous or of a pulsingnature. In one embodiment, the electric waves may have a frequency thatsubstantially matches the resonance frequency of the system comprisingthe liquid, the cavity and the piezoceramic material that may beincluded in the ultrasonic vibratable element.

According to some embodiments of the present invention the focused andscanning ultrasonic vibratable element may be adapted to cause liquid tovibrate at a preselected frequency or frequency range.

According to further embodiments the focused and scanning vibratableelement may include a piezoceramic ring at least partially coated on theouter surface with a conducting material, and having various shapes, forexample, cylindrical, convex, concave or tapered.

Some embodiments of the present invention also relate to a method forsterilization of liquid, the method including placing liquid in acontainer including at least one ultrasonic vibratable element, applyingto the vibratable element electric waves at the frequency resonance ofthe vibratable element and of the liquid and producing acousticvibration waves in the liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with theappended drawings in which:

FIGS. 1A-1E are schematic illustrations of embodiments of asterilization system;

FIGS. 2A-2B are graphic illustrations of the pressure as a function ofthe distance from the cylinder axis for a ring of piezoceramic materialaccording to an embodiment of the present invention;

FIGS. 3A-3B are schematic and graphic illustrations of a piezoceramicring including a matching layer according to an embodiment of thepresent invention;

FIG. 4 is a schematic illustration including a block diagramillustration of a sterilization system according to one embodiment ofthe present invention wherein thickness mode vibrations are applied;

FIGS. 5A-5B are schematic illustrations of a produced focused cavitationpattern in a cylindrical piezoceramic ring according to an embodiment ofthe present invention;

FIGS. 6A-6C are illustrations of various piezoceramic ring shapesaccording some embodiments of the present invention

FIGS. 7A-7B are schematic illustrations of the produced focusedcavitation pattern for a convex piezoceramic ring according to anembodiment of the present invention;

FIGS. 8A-8B are schematic illustrations of a produced focused cavitationpattern for a concave piezoceramic ring according to an embodiment ofthe present invention;

FIGS. 9A-9B are schematic illustrations of a produced focused cavitationpattern for a tapered piezoceramic ring according to an embodiment ofthe present invention;

FIGS. 10A-10C are illustrations of various rings of matching layershapes according to an embodiment of the present invention;

FIG. 11 is a schematic illustration including a block diagramillustration of a sterilization system according to a further embodimentof the present invention, wherein longitudinal and thickness vibrationsare applied;

FIGS. 12A-12B are illustrations of first and second mode longitudinalvibration wave patterns and thickness mode wave patterns according to anembodiment of the present invention;

FIGS. 13A-13C are schematic illustrations of produced cavitationpatterns in a cylindrical piezoceramic ring when applying the first modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIGS. 14A-14C are schematic illustrations of produced cavitationpatterns in a cylindrical piezoceramic ring when applying the secondmode wave pattern of longitudinal vibrations according to an embodimentof the present invention;

FIGS. 15A-15C are schematic illustrations of produced cavitationpatterns in a convex piezoceramic ring when applying the first mode wavepattern of longitudinal vibrations according to an embodiment of thepresent invention;

FIGS. 16A-16C are schematic illustrations of produced cavitationpatterns in a convex piezoceramic ring when applying the second modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIGS. 17A-17C are schematic illustrations of produced cavitationpatterns in a concave piezoceramic ring when applying the first modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIGS. 18A-18C are schematic illustrations of produced cavitationpatterns in a concave piezoceramic ring when applying the second modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIGS. 19A-19C are schematic illustrations of produced cavitationpatterns in a tapered piezoceramic ring when applying the first modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIGS. 20A-20C are schematic illustrations of produced cavitationpatterns in a tapered piezoceramic ring when applying the second modewave pattern of longitudinal vibrations according to an embodiment ofthe present invention;

FIG. 21 is a schematic illustration including a block diagramillustration of a sterilization system according to a further embodimentof the present invention, wherein vibrations that cause forces,including torsion forces, to be applied to a liquid;

FIG. 22 is illustration of the piezoceramic ring with a conducting layerwherein vibrations that cause torsion forces are applied according to anembodiment of the present invention;

FIGS. 23A-23D illustrate a further embodiment of the sterilizationsystem wherein at least two piezoceramic rings are connected on line;

FIGS. 24A-24B illustrate a further embodiment of the sterilizationsystem wherein at least two piezoceramic rings are connected on line ina vessel;

FIGS. 25A-25B illustrate a further embodiment of the sterilizationsystem wherein several piezoceramic rings are connected in parallel;

FIGS. 26A-26C illustrate a further embodiment of the invention whereinsterilization system is placed at the connection between online tubes;

FIG. 27 illustrates a further embodiment of the invention wherein thesterilization system is placed at the entrance and exit of a liquidreservoir;

FIGS. 28A-28B illustrate a further embodiment of the sterilizationsystem wherein the piezoceramic ring is movable;

FIG. 29 illustrates a further embodiment of the sterilization systemwherein the sterilization system is placed at the entrance and exit of aliquid pump;

FIGS. 30 illustrates a further embodiment of the sterilization systemwherein the piezoceramic ring is places around a filter for liquids;

FIGS. 31-32 are microbiological examination reports; and

FIG. 33 is a block diagram illustration of a liquid sterilizationchamber according to an embodiment of the preset invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following description, various aspects of the invention will bedescribed. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe invention. However, it will also be apparent to one skilled in theart that the invention may be practiced without the specific detailspresented herein. Furthermore, well known features may be omitted orsimplified in order not to obscure the invention.

Embodiments of the invention are directed towards methods andapparatuses for liquid sterilization. Embodiments of the inventionprovide methods and systems for the sterilization of non-flowing andflowing liquid.

Embodiments of the present invention may be directed towards anultrasonic vibratable element. Such a vibratable element may include apiezoceramic material. The piezoceramic material may be selected from agroup of piezoceramic materials including, but not limited to PZT-4,PZT-8, APC840, APC841, APC850, APC855, APC880 and APC856. However itshould be noted that the vibratable element of embodiments of thepresent invention is not limited to include a piezoceramic material andother suitable material may also be used.

Reference is now made to FIG. 1A and 1B, which illustrate a longitudinalcross section of one embodiment of a sterilization system 1. In theembodiment shown, sterilization system 1 may include a power supplysystem 6, for thickness mode vibration, and a container 29. Thecontainer 29 may be adapted to contain liquid 4, for example water,milk, juice, and any other thin or viscous liquid which may be consumed.The container 29 may include an ultrasonic vibratable element 2. Thevibratable element 2 may include a piezoceramic material, such as PZT-4or PZT-8 (Morgan Matroc Inc. Bedford Ohio) or any other piezoceramicmaterial for example APC840, APC841, APC850, APC855, APC880 and APC856(American Piezoceramic Inc.) and others.

FIGS. 1A and 1B present an embodiment of the invention for thesterilization of flowing liquid. The container 29 may be, for example, atube 30 having a ring of piezoceramic material 2 but may have othershapes as required. Container 29 is typically made of rubber, plastic,silicone or metal but may be made of any other suitable material. Theultrasonic vibratable element 2 may be coated with a conducting material5. The conducting material 5 may be selected from a group of conductingmaterials including, but not limited to, silver, gold, nickel,conducting rubber or any other compatible conducting material.

The vibratable element 2 may be attached to the inner portion of tube 30as in FIG. 1A or to the outer portion of tube 30 as in FIG. 1B or it maybe fitted between an inner tube and an outer tube substantiallysurrounding the inner tube, as illustrated in three dimensions in FIG.1C. The minimal thickness of the vibratable element 2, illustrated byR-r, may be in the order of 0.05 mm to 0.1 mm and the maximal thicknessmay be in the order of 20-50 mm. The inner radius of the vibratableelement 2(r) may be in the order of 1-100 mm. The length of thevibratable element may be in the order of 1-1000 mm. Other dimensionsmay be applied.

FIGS. 1D and 1E present another embodiment of the invention for thesterilization of non-flowing liquid. Container 29 may be a vessel 31,which may be a cylindrical tube closed at least at one end to contain asubstantially non-flowing body of liquid. Vessel 31 may include avibratable element 2. The vibratable element 2 may be attached, forexample, to the outer or inner portion of the cylindrical section ofvessel 31 or between an inner tube and an outer tube substantiallysurrounding the inner tube, as present in FIGS. 1D and 1E. Vessel 31 maybe made of rubber, plastic, silicone, metal, glass, etc. Alternatively,vessel 31 may be made of any other suitable material, for examplepiezoceramic material. The Vessel 31 may be open or closed at least atone side as illustrated in FIGS. 1D and 1E. Vessel 31 may furtherinclude an outer layer 33. The outer layer 33 may include an adsorbingmaterial 33 such as rubber, silicone, polymer or metal or any othersuitable absorbing material. The absorbing material 33 may be adapted toabsorb the acoustic vibrations, such that the overall system remainsstable.

Power supply system 6 may be adapted to supply electric input to thevibratable element 2. The frequency of the electric input may beselectively controlled.

Electric input from the power supply 6 may be delivered to theconductive material of the vibratable element 2, which may then causesubstantially ultrasound waves in the vibratable element 2. For example,the electric input delivered to the vibratable element 2 may causethickness waves, longitudinal waves, waves that cause torsion invibratable element 2 or any other acoustic waves.

In one embodiment of the invention, the sterilization may be achieved bysupplying electric waves from the power supply system 6 to thevibratable element 2 in a direction that is substantially through thethickness of vibratable element 2. In this embodiment the selectedfrequency or frequency range of the electric waves supplied to thevibratable element 2 by the power supply system 6 may be in the MHzrange. The selected frequency may be dependent upon various system 1parameters, including, but not limited to the thickness of thevibratable element (e.g. the ceramic thickness of the piezoceramicmaterial). For example, the frequency applied to a piezoceramic ring 2with a thickness of 0.05 mm may be approximately 20 MHz and thefrequency applied to a piezoceramic ring 2 with a thickness of 50 mm maybe approximately 0.1 MHz. Other frequencies and thicknesses may beselected.

In one embodiment of the invention the sterilization may be achieved byapplying a combination of two or more frequencies or frequency patternsof electric waves. For example, electric waves having a frequency in theKHz range may be supplied in the longitudinal direction, i.e., parallelto the length of the vibratable element 2. Electric waves having afrequency typically in the MHz range may be supplied trough thethickness of the vibratable element 2 as was described above for thethickness sterilization system. The frequency of the KHz electric wavesmay depend upon the thickness and length of the piezoceramic ring, andis typically between 20-500 KHz. Other frequencies and thicknesses maybe selected.

In one embodiment of the invention, the sterilization may be achieved byapplying a combination of three or more frequencies of frequencypatterns of electric waves. The first two wave patterns may be suppliedin the substantially longitudinal sterilization system, described above,e.g. the thickness waves and the longitude waves. The third wave patternmay be in the KHz range, typically between 15 to 300 KHz and may appliedsubstantially through the thickness of the vibratable element 2 inaddition to the two wave patterns supplied to the longitudinalsterilization system.

In response to the electric input generated by power supply system 6,the vibratable element 2 may oscillate, and may focus the center of thevibrating elements ultrasonic waves as depicted by arrow 36. Forexample, in response to the electric input the piezoceramic materialthat may be included in the vibratable element 2 may ultrasonicallyvibrate. These focused ultrasonic waves may initiate pressures in excessof several atmospheres, or bars, within the liquid, which pressures maycause the sterilization of the liquid 4. Without limiting the inventionin any way, the sterilization of the liquid may be explained by thefollowing: the progression of the ultrasound waves may create negativepressure in the liquid. The negative pressure may cause cavitationbubbles 18 (FIGS. 1A-1E) in the liquid to form. The cavitation bubbles18 may expand to an unstable size, and may eventually collapse. Thecollapse of the cavitation bubbles may generate relatively high pressureand temperature in the liquid that may lead to the breakage ofmicroorganisms, and thus may lead to the sterilization of the liquid.Furthermore, pressure within the liquid caused by resonance of highfrequency ultrasonic vibrations may also contribute the destruction ofmicro-organisms within the liquid.

Reference is now made to FIGS. 2A and 2B, which are graphicillustrations of the pressure as a function of the distance from thecylinder axis of a ring of piezoceramic material, according to anembodiment of the present invention. The pressure data was measured fora system including a cylindrical container 29, having an innerpiezoceramic ring 2 with an outer radius of r=20 mm, and which containswater, as described in FIGS. 1A through 1E. This pressure may developdue to vibration waves as depicted by arrow 36 that may be generated bypiezoceramic ring 2 as illustrated in FIG. 1.

In FIG. 2A, electric waves having a frequency of 1.25 MHz and apotential of 1 Volt, which may be the resonance frequency of apiezoceramic material, may be supplied to the vibratable element 2.Other frequencies may be used as appropriate. The electric wavessupplied in this frequency may generate a pressure of approximately 2atmospheres in the piezoceramic material (R-r in the graph) and thepiezoceramic material may oscillate. The oscillation may causevibrational waves, as depicted by arrow 36 in FIG. 1, in the liquid,causing a pressure of approximately 2.5 atmospheres in the water at themiddle axis (R=0) of container 29.

In FIG. 2B, the frequency of the electric waves may be 1 MHz, at apotential of 1 Volt, which may frequency may be the system's resonantfrequency. The system frequency resonance is the frequency at which aresonance may be achieved for the piezoceramic material and the waterfor specific physical conditions of the system. As a result of thesupplied system resonance frequency a pressure of above 8 atmospheresmay develop in the water at the middle axis (R=0) of container 29.

By matching the supplied frequency to the system resonance frequency thepressure developed in the water at the middle of the container mayconsiderably higher than when the frequency matches the piezoceramicmaterial resonance alone. Thus, the highest efficiency of sterilizationmay be achieved when the electric input is compatible to the systemfrequency resonance.

Reference is now made to FIGS. 3A-3B which are schematic and graphicillustrations of a vibratable element including a matching layeraccording to an embodiment of the present invention.

FIG. 3A is a longitude cross section of a part of container 29.Container 29, which contains liquid 4, comprises a vibratable element 2,with additional inner layers of matching material 3 and an outer tube30. The matching material may be silicone, but can be any othercompatible material. The matching material may be constructed as one ormore layers, as illustrated in FIG. 3A, on the inner side of thevibratable element 2. Each layer of matching material may have adifferent thickness or may be made of a different kind of material ormaterials. The matching layer may also be an inner tube. The thicknessof the matching layer may depend on the thickness of the vibratableelement 2, on the thickness of the piezoceramic material includedtherein, and/or on the applied frequency. According to some embodimentsthe thickness of the matching layer is typically between 0.1 to 100times the thickness of the vibratable element 2. According to furtherembodiments of the present invention the thickness of the matching layeris typically between 0.1 to 100 times the thicknesses of the ceramiclayer. FIG. 3B is a graphical illustration of the pressure inatmospheres, generated within a container 29 with a radius of R=20 mm,having a vibratable element 2 and a layer of matching material 3 andwhich contains water, as described in FIG. 3A. This pressure may bedeveloped due to vibration waves as depicted by arrow 36 in FIG. 3Aprogressing through the thickness of piezoceramic ring, and through thewater.

The layer of matching material 3 may be adapted to gradually reduce thevelocity of the vibrational waves between the velocity of the wave inthe piezoceramic material (which may be approximately 3500-4500 m/secbut may be any other frequency) and the velocity of the wave in theliquid (which is for water 1560 m/sec), thus potentially minimizing theloss of energy due to drastic velocity changes.

By adding a layer of matching material between the piezoceramic ring andthe water, and applying a signal of 1.1 MHz at a potential of 1 Volt, apressure of approximately 12 atmospheres may be developed in the middleportion of the container. This pressure may be considerably higher thanthe pressure of 2.5 atmospheres developed when using a ring ofpiezoceramic material alone as illustrated in FIG. 2A.

Reference is now made to FIG. 4, which is a schematic illustrationincluding a block diagram illustration of a sterilization systemaccording to one embodiment of the present invention wherein thicknessmode vibrations are applied. Sterilization system 1 may include acontainer 29 with liquid 4 therein. Container 29 surrounds a vibratableelement 2 including a piezoceramic material that is coated on the outerside, by a conducting material. The conducting material may beoperatively connected to a power supply system 6.

Power supply system 6 may include the following: a pulse power supply 8,a MHz power supply 14, an amplifier 16, a controller 12, and a sensingdevice 10. Pulse power supply 8 may be adapted to provide electric wavesto the piezoceramic vibratable element 2, possibly after amplificationby amplifier 16. Sensing device 10 may be adapted to sense varioussystem parameters, for example the sensing device 10 may be adapted tosense the resulting oscillation frequencies in the liquid. Controller 12may be configured to receive input from sensing device 10 (e.g.oscillation frequencies in the liquid) and may issue control signal tothe power supply 14 to supply electric waves having a desired frequencyfor obtaining frequency resonance in the vibratable element 2 and theliquid 4, thus possibly achieving high pressure in liquid 4 at themiddle axis of container 29. The power supply system 6 may or may notsupply a signal at a resonance frequency of the vibratable element 2 andthe liquid 4. In alternate embodiments the sensing device 10 need not beused or may be omitted altogether.

Reference is now made to FIGS. 5A and 5B, which are schematicillustrations of a produced cavitation pattern in a cylindricalpiezoceramic ring according to an embodiment of the present invention.Cavitation pattern 18 produced for a cylindrical piezoceramic ring 2used in the sterilization system described in FIG. 4. Other embodimentsare possible as well, as will be described in greater detailhereinbelow.

FIG. 5A illustrates a longitudinal cross-section of tube 30, with liquidentering through the upper portion of the tube as depicted by arrow 20,and flowing through the tube 30. The power supply system 6 may beadapted to supply electric waves to a cylindrical piezoelectric ring 2of tube 30. The supplied electric waves may cause vibrationaloscillations as depicted by arrows 36, progressing from the piezoceramicring 2 through the liquid 4. When a cylindrical shaped piezoceramic ringis used, the vibrations may be in the horizontal axis only. As a resultof these vibrations, a high pressure area and cavitation bubbles 18, maybe built up particularly, but not exclusively, in the middle region oftube 30. The high pressure and the cavitation may lead to thesterilization of the liquid 4 in the middle region of the tube 30. Thus,sterile liquid depicted by arrow 24, may exit the tube 30. Any liquidexisting outside the cavitation and focus pressure region, as depictedby arrow 22, will not necessarily be sterilized. The size of the area ofsterilized liquid 18 is dependent upon the voltage and frequency of thevibratable element 2.

FIG. 5B illustrates a horizontal cross section of the tube 30. Thepiezoceramic ring 2 may vibrate as a result of the electric wavessupplied by the power supply system 6, and the vibrations depicted byarrows 36 may progress through the liquid 4 toward the middle section ofthe tube where high pressure and cavitation bubbles 18 may occur. In thecase of a cylindrical piezoceramic ring, the horizontal cross section ofthe cavitation bubbles 18 may be a round circle in the center of tube 30having a smaller diameter than the tube 30.

FIGS. 6A, 6B and 6C are illustrations of various piezoceramic ringshapes according some embodiments of the present invention. Container 29or tube 30 and piezoceramic ring 2 may be further configured in anyother suitable shape. With the various shapes different cavitationpatterns are achieved, as will be further discussed hereinbelow.

FIG. 6A is a longitudinal cross-section of a convex piezoceramic ring 2according to some embodiments of the present invention, FIG. 6B is alongitudinal cross-section of a concave piezoceramic ring 2 according tosome embodiments of the present invention, and FIG. 6C is a longitudinalcross-section of a tapered piezoceramic ring 2 according to someembodiments of the present invention. Each of these rings may beattached to an inner or outer portion of a container and may beconnected to a power supply system 6.

FIGS. 7A-7B are schematic illustrations of the produced cavitationpattern for a convex piezoceramic ring according to an embodiment of thepresent invention. According to the present embodiment, a convexpiezoceramic ring 2 may be used in the thickness mode sterilizationsystem described in FIG. 4. The longitudinal and horizontal crosssections of the convex piezoceramic ring are illustrated in FIGS. 7A and7B.

Liquid may enter the upper portion of tube 30, as depicted by arrow 20,and may flow through it. The power supply system 6 may supply electricwaves to the convex piezoceramic ring 2 in tube 30. The suppliedelectric waves may cause vibrational oscillations depicted by arrows 36,which may progress through the piezoceramic ring 2 and through theliquid 4. These vibrations may progress not only in the horizontal axis,as in the cylindrical piezoceramic ring, but also in other directions.As a result of these vibrations, an oval shaped high pressure area andcavitation bubbles 18 may be built up in the middle region of the tube.The high pressure and the cavitation may lead to the sterilization ofthe liquid in the oval region. Thus sterile liquid depicted by arrow 24may exit the tube. The liquid 4 existing outside the cavitation region,as depicted by arrow 22, may not necessarily be sterile.

FIG. 7B illustrates a horizontal cross section of the convexpiezoceramic ring. The convex piezoceramic ring 2 may vibrate as aresult of the electric waves that may supplied by the power supplysystem 6, and the vibrations depicted by arrows 36 may progress throughpiezoceramic 2 and through liquid 4 toward the middle portion of thetube 30 where high pressure and cavitation bubbles 18 may occur. For theconvex piezoceramic ring shape the horizontal cross section of thecavitation region may be a round circle in the center of the tube 30having a smaller diameter than the tube.

FIG. 8 illustrates a produced focus cavitation pattern according toanother embodiment of the invention, wherein a concave piezoceramic ring2 is used in the thickness mode sterilization system described in FIG.4. The longitudinal and horizontal cross sections of the concavepiezoceramic ring are illustrated in FIGS. 8A and 8B.

The system is similar to that described in FIGS. 7A and 7B. For theconcave piezoceramic ring 2, the vibrations, depicted by arrow 36 may bein the horizontal axis as well as in other directions. The cavitationbubbles 18 may be obtained in a long narrow region at the middle portionof the tube 30. In the horizontal cross section of the concavepiezoceramic ring 2 the cavitation bubbles 18 may be obtained in a smallround circle in the middle portion of tube 30.

FIGS. 9A and 9B, illustrate the produced cavitation in a longitudinaland horizontal cross-section, according to another embodiment of theinvention, wherein a tapered piezoceramic ring 2 is used in thethickness mode sterilization system described in FIG. 4.

The system is similar to that described in FIGS. 7A and 7B. For thetapered piezoceramic ring 2, the vibrations, depicted by arrow 36, maybe in the horizontal axis as well as in other directions. The cavitationbubbles 18 may be obtained in a narrow conic region at the middleportion of the tube 30. In the horizontal cross section of the taperedpiezoceramic ring 2 the cavitation bubbles 18 may be obtained in a smallround circle in the middle portion of the tube.

Reference is now made to FIGS. 10A-10C illustrating three furtherembodiments of the invention for various shapes of matching materiallayer. FIG. 10A illustrates tapered shape matching material layer, FIG.10B illustrates concave shape matching material layer and FIG. 10Cillustrates convex shape matching material layer. It will be appreciatethat the layer of matching material 3 may be further configured in anyother shape. FIGS. 10A-10C are a longitude cross section of half tube 30(from R=0 to R) having a cylindrical vibratable element includingpiezoceramic material 2, and including an inner layer of matchingmaterial 3. The vibratable element 2 may vibrate as a result of theelectric waves supplied by the power supply system 6, and thevibrations, depicted by arrows 36, may progress through the liquid wherehigh pressure and cavitation bubbles 18 may occur. Here the variousshapes of cavitation 18 may be achieved by the addition of variousshapes of matching layers 3 on the inner side of the piezoceramic ring 2similarly to the cavitation patterns that may be achieved by changingthe shape of the vibratable element 2 itself, as was illustrated above.

Reference is now made to FIG. 11, which illustrates a diagram of afurther embodiment of the sterilization system. In the longitudinalsterilization system waves that are in longitudinal direction to thevibratable element 2 may be supplied. These waves may be supplied inaddition to the waves that may be applied through the thickness of thevibratable element 2 in the thickness sterilization system. This mayprovide a scanning pattern of focused cavitation bubble area 18.

Sterilization system 1 may include container 29 with liquid 4 therein.Container 29 may have an inner or outer vibratable element 2 that may becoated with a conducting material and may be connected to a power supplysystem 6.

The power supply system 6 may include of the following: a pulse powersupply 8, MHz and KHz power suppliers 14 and 15 respectively, a mixer17, a controller 12 and an amplifier 16. Power supply system 6 mayinclude other parts suitable for supplying electric waves to vibratableelement 2.

A pulse power supply 8 may be adapted to supply electric waves having aninitial frequency, the MHz power supply 14 may be adapted to supplyelectric waves at a frequency that may be required for generatingthickness waves described in FIG. 4 and the Kilohertz (KHz) power supply15 may be adapted to supply electric waves at a frequency typically in arange of 50-500 KHz for generating the longitudinal waves. Thecontroller 12 may be adapted to control the MHz power supply so as toachieve the resonance frequency in the thickness mode system. Mixer 17may be adapted to group the MHz and KHz waves to a combined wave thatmay enter the vibratable element 2 after amplification by the amplifier16.

The vibratable element 2 may oscillate in response to the combinedelectrical input. The MHz power supply 14 may cause thickness waves (notshown) and the KHz power supply 15 may cause longitudinal or bendingwaves 38. These waves when operating together may provide various shapesof cavitation regions, as will be described hereinbelow. Pulse powersupply 8 and controller 12 may operate, similarly as was described forFIG. 4, to supply a combination of KHz and MHz electric waves that mayhave a frequency which may the frequency resonance of vibratable element2 and the liquid 4.

FIGS. 12A and 12B are schematic illustrations of longitudinal vibrationwave patterns according to an embodiment of the present invention. Twowave patterns 37 and 39, which will be referred as the first and secondmode of the longitudinal vibrations respectively, are presented. In thesecond mode of vibration, wave pattern 39, the frequency of the waves isdouble the frequency of the waves in the first mode, wave pattern 37.These wave patterns may be obtained in the vibratable element 2 and inthe liquid 4 by a combination of the longitudinal vibrations with thethickness vibrations, for the cylindrical piezoceramic ring 2configuration of the sterilization system 1 (As is shown in FIGS.1A-1E). Other wave patterns may be used.

Reference is now made to FIGS. 13A-13C which are schematic illustrationsof produced cavitation patterns in a cylindrical piezoceramic ring whenapplying the first wave pattern of longitudinal vibrations according toan embodiment of the present invention.

FIG. 13 is a longitudinal cross section of container 29 with liquid 4,having a vibratable element 2. A cavitation bubble 18 pattern may beproduced as a result of the first mode longitude vibrations 37 that maybe applied by the power supply system 6.

In FIG. 13A, the positive amplitude of the first wave pattern 37 and thecorresponding cavitation bubbles 18 are illustrated. In FIG. 13B, thenegative amplitude of the first wave pattern 37 and the correspondingcavitation bubbles 18 are illustrated. In FIG. 13C the cavitationbubbles 18 may be achieved in a tube having a cylindrical piezoceramicring 2 by the whole longitudinal vibration wave are illustrated. Whileapplying first mode longitudinal vibration to the thickness modesterilization system, a scanning pattern of the focused cavitation areamay be achieved.

FIGS. 14A-14C are schematic illustrations of produced cavitationpatterns in a cylindrical piezoceramic ring when applying the secondwave pattern of longitudinal vibrations according to an embodiment ofthe present invention. Here, similarly to FIG. 13, a cavitation bubblepattern 18 may be produced as a result of the second mode longitudinalvibrations 39.

In FIG. 14A, the positive amplitude of the second wave pattern 39 andthe corresponding cavitation bubbles pattern 18 are illustrated. In FIG.14B, the negative amplitude of the second wave pattern 39 and thecorresponding cavitation bubbles pattern 18 are illustrated. In FIG. 14Cthe cavitation bubbles pattern 18 obtained in tube 30 by the wholelongitudinal vibration wave 38 is illustrated. While applying secondmode longitudinal vibration to the thickness mode sterilization system,a scanning pattern of the focused cavitation area may be achieved. Othermodes of longitudinal vibration may be used.

FIGS. 15-20 are schematic illustrations of produced cavitation patternsthat may be produced using various shapes of piezoceramic rings and whenapplying the first wave pattern of longitudinal vibrations, according toan embodiment of the present invention. In FIGS. 15 and 16 the convexpiezoceramic ring shape is used, in FIGS. 17 and 18 the concave shape isused and in FIGS. 19 and 20 the tapered shape is used.

In FIGS. 15, 17 and 19 a cavitation bubble pattern 18 may be produced asa result of the first mode longitude vibrations 37 similarly to FIG. 13.

In FIGS. 16, 18 and 20 a cavitation bubbles pattern 18 may be producedas a result of the second mode longitude vibrations 39.

Reference is now made to FIG. 21 which is a schematic illustrationincluding a block diagram illustration of a sterilization systemaccording to a further embodiment of the present invention, whereinvibrations that causes torsion forces are applied. Waves that causetorsion forces may be applied through the thickness of the piezoceramicring in addition to the thickness mode vibrations and the longitudinalmode vibrations.

FIG. 22 is an illustration of the piezoceramic ring wherein vibrationsthat causes torsion forces are applied according to an embodiment of thepresent invention. In order to achieve torsion forces the conductinglayer 5, coated on the vibratable element 2 may include one or moreportions of non-conducting material as illustrated. The non-conductingmaterial may be applied to at least a portion of the inner surfaceand/or outer surface of the vibratable element 2. This may be achieved,for example, by cutting the conducting layer and exposing strips ofnon-conducting piezoceramic material 2, other method for includingnon-conducting material may be used. The torsion forces that may thus beachieved are depicted by arrow 25. Since the conducting layer may haveportions of non-conducting material, it may be desirable to have theelectric wires 7 in contact with each section of the conducting material5, such that power may be supplied to the whole vibratable element 2.

The torsion forces may be achieved in the cylindrical piezoceramic ringas illustrated in FIG. 22 as well as in other shapes of piezoceramicrings 2, such as, for example, convex, concave and tapered piezoceramicrings.

FIGS. 23A-23D illustrates a further embodiment of the sterilizationsystem wherein at least two piezoceramic rings are connected on line.The piezoceramic rings 2 may have various shapes and may be connected tothe thickness sterilization system as described in FIG. 4 as well as tothe longitudinal and torsion sterilization system as described in FIG.11 and 21, respectively. In some embodiment of the present invention theon-line vibratable elements 2 may be connected together to the samepower supply system as illustrated, alternatively, one or morevibratable elements 2 may be connected to a different power supplysystem (not shown). The piezoceramic rings 2 may all be constructed fromthe same piezoceramic material or each ring may be constructed from adifferent piezoceramic material. By connecting various shapes ofpiezoceramic rings 2 along the tubes a selective sterilization may beachieved since, as was illustrated hereinabove. the piezoceramic ringshape influence the cavitation pattern.

FIGS. 24A-24B illustrate a further embodiment of the sterilizationsystem wherein at least two piezoceramic rings are connected on line ina vessel. The vibratable element 2 may be of various shapes asillustrated in FIG. 24A and 24B and may be connected to the thicknesssterilization system as described in FIG. 4 as well as to thelongitudinal or torsion sterilization systems as described in FIG. 11and 21 respectively. All the on-line vibratable elements 2 or vibratableelement's portions may be connected together to the same power supplysystem 6. Alternatively, each vibratable element or portion 2 may beconnected separately to a different power supply system 6. Vibratableelement 2 may all be constructed from the same piezoceramic material oreach ring or portion may be constructed from a different piezoceramicmaterial or for a non-piezoceramic material. Different sterilizationmodes may be applied to each vibratable element 2 or to each portion.

FIGS. 25A-25B illustrate further embodiment of the sterilization systemwherein several piezoceramic rings are parallely connected. FIG. 25Aillustrates a vertical cross section of tube 30 including vibratableelements 2 wherein each tube may be separately connected to power supplysystem 6. The void 32 between tube 30 and the vibratable element 2 maybe filled with a material such as rubber, plastic, silicone or cork orany other suitable material. Tube 30 may be made of rubber, plastic,silicone, metal or any other suitable material. A thickness,longitudinal or torsion sterilization system may be operated. All theparallel vibratable elements 2 may be connected together to the samepower supply system 6, alternatively, one or more vibratable element 2may be connected to a different power supply system 6.

Tube 30 may include piezoceramic material having cavities thus creatingsmall tubes wherein liquid can flow. These cavities may have any shapedescribed above or any other suitable shape. The cavities may have adiameter range of preferably 0.1-1 micron; other dimensions may also beused. The power supply system may be connected to the tube which may becoated with a conducting layer.

FIGS. 26A-26C illustrate a further embodiment of the invention whereinsterilization system may be placed at the connection between tubes 30.In FIGS. 26A, 26B and 26C sterilization system 1 including vibratableelement or elements 2 may be placed at the connection of two tubes,three tubes and four tubes respectively. Vibratable element 2 may haveany shape discussed above or any other suitable shape. The vibratableelement 2 may be operated according to any of the modes discussedhereinabove.

FIG. 27 illustrates a further embodiment of the invention wherein thesterilization system may be placed at the entrance and exit of a liquidreservoir. Liquid reservoir 50 contains liquid that may be circulatingthrough the sterilization system as depicted by arrows 51. Thecavitation created by the sterilization system may destroy bacteria,protozoa and larvae in the liquid as well as other particles existing inthe liquid. Vibratable element 2 may have any shape discussed above orany other suitable shape. The vibratable element 2 may be operatedaccording to any of the modes discussed hereinabove.

FIGS. 28A-28B illustrate a further embodiment of the sterilizationsystem wherein the vibratable element may be movable. Vibratable element2 may be placed inside a reservoir 40. The reservoir 40 may containliquid 4, connected on the outer side to a bar 41, that may emerge fromthe liquid reservoir. Bar 41 may be connected to a device that may allowits moving on the horizontal and/or vertical axis thus the vibratableelement 2 may move inside liquid reservoir 40. The maneuverability ofthe vibratable element 2 may allow the sterilization of all the liquid 4in the reservoir 40. The vibratable element 2 may be connected to thepower supply system 6 through the bar 41. FIGS. 28A illustrates anembodiment wherein the vibratable element 2 may be parallel to thehorizontal axis while FIG. 28B illustrates an embodiment wherein thevibratable element 2 is perpendicular to the horizontal axis. Vibratableelement 2 may have any shape discussed above or any other suitableshape. The vibratable element 2 may be operated according to any of themodes discussed hereinabove.

FIG. 29 illustrates further embodiment of the invention whereinvibratable element 2 of sterilization system 1 are connected at theentrance and exit of a liquid pump 42 for the sterilization of thepumped liquid. Vibratable element 2 may have any shape discussed aboveor any other suitable shape. The vibratable element 2 may be operatedaccording to any of the modes discussed hereinabove.

FIG. 30 illustrates further embodiment of the invention wherein thevibratable element 2 of sterilization system 1 is placed on the outerside of a commercially available liquid filter 43 for the sterilizationof the liquid while filtering through the filter. In this case, liquidsterilization and filter cleaning may be performed substantiallysimultaneously. The vibration of the filter, for example by thepiezoceramic element, may be adapted to prevent bio-films formation inthe filtering system. Any shape of piezoceramic of vibratable elementsdiscussed above may be used. Vibratable element 2 may have any shapediscussed above or any other suitable shape. The vibratable element 2may be operated according to any of the modes discussed hereinabove.

Reference is made now to FIG. 33, which is a diagrammatic illustration(cross section) of a sterilization chamber in accordance with anembodiment of the present invention. The sterilization chamber 3300 maybe adapted to contain a liquid such as water or any other liquid to betreated. The container may be cylindrically shaped, or may be of anyother shape. The chamber 3300 may include an outer section 3302 and aninner section 3004. The inner section 3304 and outer sections 3302 mayalso be cylindrically shaped. For convenience purposes, the liquidwithin the inner tube 3304 will be referred to as “volume B” and theliquid outside the inner tube 3304 will be referred to as “volume A”.The chamber 3300 may further include a vibrating or vibratable element3306. In some embodiments of the present invention, such as the oneshown in FIG. 33, two or more vibrating or vibratable elements 3306 maybe used. The vibratable elements 3306 may be constructed according toany of the vibratable elements described above. The vibratable elements3306 may be attached to either an inner or outer wall of the innersection 3304. In this configuration, the location of the vibratableelements 3306 with respect to volume B may correspond to theconfiguration described in FIG. 1B, i.e. the vibratable element 3306 isattached to the outer portion of the inner section 3304. However, inother embodiments, the vibratable elements 3306 may be attached to theinterior surface of the inner tube 3304. The chamber may also includematching layers (not shown) located and operated in accordance with anyof the discussions above.

The chamber may be connected to a power supply and signal generator. Thepower supply and signal generator may be operatively connected to thevibratable elements. The power supply and signal generator may beconstructed in accordance with any of the configurations describedabove.

A liquid may enter the chamber 3300 through an opening 3312 from anouter source (not shown) to the portion labeled volume A, on either sideof the outer section 3302, where the vibratable elements 3306 may beoperated as described hereinabove, thereby causing acoustic vibrationaloscillations in the liquid. Vibrations from the element 3306 in theouter direction may be reflected from the chamber's wall and may createstanding acoustical pressure waves. This may initiate at least a partialliquid sterilization. The oscillation frequency of the vibratableelements 3306 element may be selected, such that the oscillation of thevibratable elements 3306 may cause standing waves in the liquid.

The liquid may proceed into the inner section 3304, labeled volume B,initiation focused acoustic pressure waves as described hereinabove withreference to FIG. 1B. Vibratable elements 3306 may also produce standingwaves, possibly simultaneously affecting the liquid in volume A as wellas the liquid in volume B, and further sterilizing the liquid to providea substantially sterilized liquid. The liquid may leave the chamber 3300through an opening 3314 at the end of the inner section 3304. In thisembodiment a single vibratable element 3306 may provide vibrationalacoustic waves both in inner and outer directions, this may allow higheraffectivity of the sterilization system for example by enhancing thevolume of liquid to be sterilized using a single vibratable elements.According to other embodiments multiple may be used (as is shown inFIGS. 26A-26C) this may be suitable where substantially large volumes ofwater are to be sterilized. Other benefits may exist. Vibratable element2 may have any shape discussed above or any other suitable shape. Thevibratable element 2 may be operated according to any of the modesdiscussed hereinabove.

EXPERIMENTAL RESULTS

An experimental system was built from a 12 mm diameter cylindrical ringof a piezoceramic material PZT-4 with a thickness of 2 mm and a lengthof 20 mm. Water was flowing through the ring at a capacity of 1 cm/sec.The water contained an initial microbial concentration of bacteria pervolume. The ring was connected to a power supply system as described inFIG. 4 or to a power supply system as described in FIG. 11 or FIG. 21. Amicrobial test was conducted before and after operation of thesterilization system.

The first microbial test was conducted by AminoLab Laboratory anofficially recognized laboratory by Ministry of Agriculture, in Israel,according to the “Standard Methods for the Examination of Water andWastewater” using the pour plate technique.

FIG. 31 set forth the experimental results for the experimental systemand method described above. Six samples—M02524, M02525, M0526, M0527,M0528 and M0529 were detected. Sample M02524 is the control samplecontains untreated examined water with initial bacterial count of9.8×10⁴ CFU/ml. Samples M02526, M02527, M02528 are water exiting theexperimental system described above after the operation of thicknesssterilization system as described in FIG. 4. The bacteria count of thesesamples was 8.7×10⁴, 7.0×10⁴, and 5.1×10⁴ CFU/ml respectively. SampleM02525 is water exiting the experimental system described above afterthe operation of the longitudinal sterilization system as described inFIG. 11. The bacteria count of this sample was 1.3×10³ CFU/ml. SampleM02529 is water exiting the experimental system described above afterthe operation of the torsion sterilization system as described in FIG.21. The bacteria count of this sample was <100 CFU/ml. For the samplesexiting the thickness sterilization system no significant reduction ofthe bacteria count was achieved. For sample M02525 exiting thelongitudinal sterilization system a reduction of approximately 2 ordersof magnitude was achieved in the bacteria count. For sample M02529exiting the torsion sterilization system where thickness, longitude andtorsion vibrations were applied, a reduction of more than 3 orders ofmagnitude was achieved in the bacteria count.

A second microbial test that includes a bacteria count and a mold countwas conducted by MicroLab Laboratories, Rehovot, an officiallyrecognized laboratory by Ministry of Agriculture, in Israel. Thebacteria used were ERWINIA and CLAVIBACTER and the mold were ASPERILLUSand FUSARIUM. The Laboratory method was conducted according to the“Standard Methods for the Examination of Water and Wastewater” using thepour plate technique.

FIG. 32 illustrates the experimental results for the experimental systemand method described above, as accepted from the MicroLab Laboratories.

Six samples 1-6 were detected. Sample 6 is the control sample containsuntreated examined water with initial bacterial count of 4×10⁸ CFU/mland mold count of 4.2×10⁵ CFU/ml. Samples 3 and 4 are water exiting theexperimental system described above after the operation of thicknesssterilization system. The bacteria count of these samples was 1.2×10⁷,1.2×10⁸ CFU/ml respectively and the mold count was <10 and 3×10⁴ CFU/mlrespectively. Samples 2 and 1 are water exiting the experimental systemdescribed above after the operation of longitudinal sterilizationsystem, where the longitude mode is at the first and second mode asdescribed in FIGS. 12A and 12B respectively. The bacteria count of thesesamples was 4.1×10⁶ and 8.6×10³ CFU/ml for the first and second mode andthe mold count for both modes was <10 CFU/ml. Sample 5 is water exitingthe experimental system described above after the operation of torsionsterilization system. The bacteria and mold count of this sample were<10 CFU/ml.

For the samples exiting the thickness sterilization system nosignificant reduction of the bacteria count was achieved. For sample 2and 1 exiting the longitudinal sterilization system where longitudevibrations were applied at the first and second mode of vibration areduction of approximately 2 and 5 orders of magnitude was achieved inthe bacteria count, respectively. For both samples the mold count wasreduced to <10 CFU/ml. For sample 5 exiting the torsion sterilizationsystem a reduction of 8 orders of magnitude was achieved in the bacteriacount and the mold count was reduced to <10 CFU/ml.

The most efficient sterilization system as accepted at both laboratoriesis the system described in FIG. 21 where a combination of thickness,longitude and torsion vibrations are applied.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. An apparatus to substantially sterilize a liquid comprising: a ringof vibratable material, said ring being of an arbitrary shape andlength, and having an internal passage through which the liquid mayflow, said ring further comprising a layer of matching material disposedbetween the ring and the liquid; and a power supply system connected tosaid ring and adapted to supply electric waves to said ring at afrequency estimated to be a resonance frequency of a system formed bysaid ring and the liquid.
 2. The apparatus of claim 1, wherein saidvibratable material is comprised of a piezoceramic material.
 3. Theapparatus of claim 2, wherein said piezoceramic material is coated on atleast one surface by a conducting material.
 4. The apparatus of claim 3,wherein said electric waves cause said ring to vibrate along itsthickness.
 5. The apparatus of claim 4, wherein said electric wavescause the ring to vibrate such that standing thickness waves areproduced within the liquid.
 6. The apparatus of claim 3, wherein saidelectric waves cause said ring to produce torsion vibrations.
 7. Theapparatus of claim 6, wherein said electric waves cause said ring tovibrate such that standing torsion waves are produced within the liquid.8. The apparatus of claim 3, wherein said electric waves cause said ringto vibrate along its length.
 9. The apparatus of claim 8, wherein saidelectric waves cause said ring to produce standing longitudinal waveswithin the liquid.
 10. The apparatus of claim 1 wherein said powersupply system comprises a pulse power supplier, a MHz power supplier, anamplifier, a controller, and a sensing device.
 11. The apparatus ofclaim 10 wherein said electric waves are in the range of 0.1-20 MHz. 12.The apparatus of claim 10 wherein said power supply system furthercomprises a KHz power supplier.
 13. The apparatus of claim 10, furthercomprising a mixer to mix electric waves intended to produce thicknessvibrations and electric waves intended to produce vibrations along thering's length.
 14. The apparatus of claim 10, wherein said KHz powersupplier is adapted to produce electric waves in the range of 20 to 500KHz.
 15. The apparatus of claim 1 wherein the acoustic velocity in thepiezo material is gradually reduced to match the acoustic velocity inthe liquid to minimize energy loss, when transmitting from the piezomaterial to the liquid.
 16. The apparatus of claim 1, wherein said layerof matching material is made of silicone or plastic.
 17. The apparatusof claim 1 wherein said layer of matching material has a thickness inthe range of 0.1-10 times the thickness of said piezoceramic ring. 18.The apparatus of claim 1 wherein said layer of matching materialcomprises of more then one sub-layers made of different plasticmaterials.
 19. The apparatus of claim 1 wherein said layer of matchingmaterial has a shape selected from the group consisting of convex,concave, tapered and polygon.
 20. The apparatus of claim 1, wherein thethickness of the matching layer depends on one or more of the thicknessof the ring and on the applied frequency.
 21. The apparatus of claim 1,wherein applying a signal of 1 volt and 1 MHz frequency to the ring,causes a pressure in the middle portion of the liquid filling the ring,wherein the pressure is higher than the pressure in the ring material.22. The apparatus of claim 3, wherein the apparatus is placed at one ofthe sites consisting of the connection between at two tubes, at theentrance of a liquid reservoir, the exit of a liquid reservoir, theentrance of a liquid pump and the exit of a liquid pump.
 23. Theapparatus of claim 3, wherein the apparatus may move in horizontal andvertical axis of a liquid reservoir.
 24. The apparatus of claim 3,wherein the apparatus is placed on the outer side of a liquid filter andthereby liquid sterilization and filter cleaning may be performedsubstantially simultaneously and the vibration of the filter may beadapted to prevent biofilm formation in the filtering system.
 25. Theapparatus of claim 1 further comprising at least a second ring ofvibratable material, wherein said second ring is connected to said firstring of vibratable material.
 26. The apparatus of claim 1 comprising: asecond piezoceramic ring, wherein the first and the second ring areconstructed from the same or different piezo material, wherein the ringdimensions, shape and materials resulting in variable shapes ofcavitation area along the ring.
 27. An apparatus to substantiallysterilizing a liquid comprising: at least one container into which aliquid may enter; a first ring of vibratable material and having anarbitrary shape and length, said ring at least partially residing insideof said container and having an inner passage through which the liquidmay pass; a second ring of vibratable material; and a power supplysystem to supply electric waves to said ring.
 28. The apparatus of claim27, wherein said power supply system supplies electric waves at afrequency estimated to be a resonance frequency of a system formed bysaid ring and the liquid.
 29. The apparatus of claim 28, wherein saidpower supply system supplies electric waves at a frequency estimated tobe a resonance frequency of system formed by said ring and liquid withinthe inner passage of said ring.
 30. The apparatus of claim 28, whereinsaid power supply system supplies electric waves at a frequencyestimated to be a resonance frequency of a system formed by said ringand a volume of liquid between the outside of said ring and an innerwall of said container.
 31. The apparatus of claim 30, wherein saidpower supply system also supplies electric waves at a frequencyestimated to be a resonance frequency of a system formed by said ringand liquid within the inner passage of said ring.
 32. The apparatus ofclaim 31, wherein said electric waves cause said ring to vibrate alongits thickness.
 33. The apparatus of claim 31, wherein said electricwaves cause the ring to vibrate such that standing thickness waves areproduced within the liquid.
 34. The apparatus of claim 31, wherein saidelectric waves cause said ring to produce torsion vibrations.
 35. Theapparatus of claim 31, wherein said electric waves cause said ring tovibrate such that standing torsion waves are produced within the liquid.36. The apparatus of claim 29, wherein said electric waves cause saidring to vibrate along its length.
 37. The apparatus of claim 31, whereinsaid electric waves cause said ring to produce standing longitudinalwaves within the liquid.
 38. The apparatus of claim 31, wherein theliquid is at least partially sterilized due to vibrations produced bysaid ring.
 39. The apparatus of claim 38, further comprising a filter,wherein filter blockage is avoided due to the at least partialsterilization of the liquid.
 40. The apparatus of claim 27, wherein thefirst ring is located at the entrance to the container and the secondring is located at the exit from the container.
 41. The apparatus ofclaim 27, further comprising a second power supply system connected tosaid second ring of vibratable material.
 42. The apparatus of claim 31,wherein a liquid enters the apparatus through an opening on saidcontainer and leaves the apparatus through an opening of the innerpassage of said ring.
 43. The apparatus of claim 31, wherein a liquidenters the apparatus through an opening of the inner passage of saidring and leaves said apparatus through an opening on said container. 44.The apparatus of claim 27, wherein ring has a disk shape having cavitieswherein liquid can flow, the cavities having a shape selected from agroup consisting of cylindrical, convex, concave, and tapered.
 45. Adevice to substantially sterilize a liquid comprising: a piezoceramicring, said ring being of an arbitrary shape and length, and beingattached to an inner diameter of a tubular sterilization container,which has an internal passage with non-flowing or flowing liquid; and apower supply system connected to said ring and adapted to supplyelectric waves to said ring at a frequency estimated to be a resonancefrequency of a system formed by said ring and the liquid; therebyfocusing acoustic standing waves, wherein a cavitation column isproduced in the middle of the ring,
 46. A device to substantiallysterilize a liquid comprising: at least one container into which aliquid may enter; a piezoceramic ring having an arbitrary shape andlength, the ring disposed inside the container and having an innerpassage through which the liquid may pass; a power supply system tosupply electric waves to the ring, thereby creating a focusing standingwaves in the liquid passing through the ring and passing through thecontainer by implying the action of both piezo element sides, wherein ahigh pressure cavitation column is formed in the middle of the ring, andpressure is created in the liquid passing the inner volume of the ringand the volume between container walls and outer wall of the ring.